docs: def check_expired_activation(self, activation_key):
          """
          Check if ``activation_key`` is still valid.
  
          Raises a ``self.model.DoesNotExist`` exception if key is not present or
           ``activation_key`` is not a valid string
  
          :param activation_key:
              String containing the secret SHA1 for a valid activation.
  
          :return:
              True if the ket has expired, False if still valid.
  
          """
          if SHA1_RE.search(activation_key):
              userena = self.get(activation_key=activation_key)
              return userena.activation_key_expired()
          raise self.model.DoesNotExist